Marcos Alonso has confirmed that Chelsea have offered him a long-term contract extension and added that he expects to sign it before the end of October.

There are two years remaining on Alonso's current deal, signed when he arrived for around £24 million from Fiorentina in the summer of 2016, but Chelsea are keen to extend his stay.

Alonso established himself as a key figure at left wing-back under Antonio Conte and has transitioned well to operating on the left of a back four since Maurizio Sarri's arrival, registering one goal and two assists from defence in eight Premier League appearances this season.

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"What I can say is that I am very calm and very happy at Chelsea and that the club must be the same with me," he told Spanish newspaper AS while on international duty. "Even though I still have two years left on my current deal, they have offered me an extension. We are discussing it and talks are already advanced.

"If everything goes well, I think I will sign before the end of the month. In the coming days."

Asked how long his new contract will be, Alonso replied: "My father is the one who leads the negotiation and he is the one who deals with it. I am 27 years old, I still have two more ahead and I am going to extend my contract ... What matters to me is to play as well as possible to win games and titles with Chelsea and continue with the Spain national team. I'm calm with my contract."

Eyebrows were raised when Sarri decided to shift Alonso -- who is widely regarded as being better going forward than defensively -- from wing-back to full-back in his new 4-3-3 system, but his form has kept January signing Emerson Palmieri on the sidelines and earned him a call-up to Luis Enrique's latest Spain squad ahead of Barcelona defender Jordi Alba.

"I feel comfortable in both formations [with three at the back or four]," he added. "The system with three centre-backs is one I was used to in Italy and it went very well. I enjoyed playing as a wing-back due to the attacking exposure you have in that position. But I also like playing in Sarri's current system.

"In modern football, positioning, the shape and occupying spaces are very important. Luis Enrique insists this as well as my Chelsea manager.

"I am comfortable and I am suited to this football. My natural position is left back on a back four, but I have to be ready to help the team regarding the demands of the manager."